The present invention generally relates to a multiple station facsimile relay system, and more particularly to a multiple station facsimile relay system in which a material to be transmitted is sent from a transmitting facsimile to a receiving facsimile through relay transmission and an acknowledgment report confirming transmission of the message to the receiving facsimile is returned back to the transmitting facsimile through relay transmission.
Recently, several types of communication networks have been developed, and an increasing number of types of the communication networks is being made commercially available. However, in many cases where a facsimile communication is carried out by utilizing such communication networks, it is necessary to make use of several different communication networks for transmitting a message or image for a transmitting facsimile to a receiving facsimile via a plurality of relay stations. Generally, a communication network to which the transmitting facsimile is connected directly is different from a communication network to which the receiving facsimile is connected directly, and, in such a case, a direct transmission of the message or image from the transmitting facsimile to the receiving facsimile cannot be made without performing a relay transmission thereof via other relay station facsimiles. To carry out the above relay transmission, the relay station facsimiles used as relay stations through which the message or image is transmitted to the receiving facsimile must include a facsimile already connected to the communication network to which the transmitting facsimile is connected and a facsimile already connected to the communication network to which the receiving facsimile is connected. Conventionally, a transmitting facsimile which makes a request for relay transmission to any relay station (which transmitting facsimile is, hereinafter, called merely a transmitting station) transfers or notifies to the relay station a registered code of the transmitting station facsimile when a request for the relay transmission is made by the transmitting station to the relay station. This notification of a registered code of the transmitting station facsimile to the relay station is necessary for each relay station for sending an acknowledgment report back to each transmitting station facsimile each time a relay transmission of the message or image from one station to another is completed.
In such a conventional facsimile relay transmission method, the transmitting station merely notifies to the relay station a registered code of the transmitting station facsimile for receiving an acknowledgment report from a final relay station. If there is only one relay station which is currently in use for relay transmission, an acknowledgment report can be safely sent back to the transmitting station from the only relay station. However, if two or more relay stations are used for the relay transmission, a common communication network which is shared by both the transmitting station and a final relay station does not necessarily exist, and there is usually no suitable means for determining a path for sending a report from the final relay station to the transmitting station. Therefore, it is very difficult to send safely an acknowledgment report from the final station back to the transmitting station after the relay transmission of the message or image is completed. Conventionally, in such cases where a plurality of relay stations are used for relay transmission, an acknowledgment report often cannot be safely sent back to a transmitting facsimile from a final relay station.